A breathing mask can be equipped with or connected to a portable radio communication device in order to enable the wearer of the breathing mask to communicate with other persons. For example, a fire fighter wearing a breathing mask has to be able to communicate with other fire fighters of his team and with fire chiefs. Solutions in which a breathing mask is equipped with a radio communication device are described, for example, in publications GB2415316 and GB2421443. Power consumption of a radio communication device is a critical issue, because a battery that energizes the radio communication device should be as light and small as possible and, on the other hand, it might cause even a dangerous situation if the electrical energy stored in the battery runs out at a critical time instant and the wearer of the breathing masks is no longer able to communicate.
A radio communication device consumes power especially when transmitting a radio signal. In one solution according to the prior art, a transmission of a radio signal is constantly active and, therefore, the average power consumption of the radio communication device is very high. During a significant portion of time, the radio signal carries only such voice components that are typically of no use, e.g. breathing noise, pressurised air ventilation, and external noise. Furthermore, in conjunction with certain radio protocols, the transmission of the above-mentioned useless voice components causes unintentional reservation of protocol units as time slots, data frames, or data packets.
In another solution according to the prior art, a transmitter of a radio communication device is “push-to-talk” activated and coupled via an corded link to an control box that comprises a push button. In this case, a transmission of a radio signal is not constantly active and, therefore, the average power consumption of the radio communication device is reduced. A user of the radio communication device must push a button when talking into a microphone in order to allow the radio transmission. This requires that the user can have only one hand free while talking into the microphone. For example, for a fire fighter it is highly important that freedom of action is not excessively limited during communication, i.e. both hands should be free for other purposes also during communication. Furthermore, the control box can often frustrate the user as it may limit the action of freedom also when there is no communication or it has to be placed to a pocket or some other suitable place when not used.